If by spark you mean, how to feel butterflies in your stomach at the mere thought of them or to feel the hairs raise on the back of your neck whenever they enter the room - it won't really happen that way again.
The honeymoon phase of your relationship is likely over. This isn't a bad thing, it's completely normal. That phase only lasts from three months to three years in any relationship. It looks like the two of you have embarked on the new phase which is mature love. This however, does not mean that you can't have more fun, exciting and sexy times with each other. It just means you'll be connecting on a new level.
Keeping things fun and interesting will help to keep your connection strong. Don't get lazy or too comfortable and don't let him get that way either. Maintain your appearance - it sounds shallow but it's not - men are visual creatures and your ability to take care of yourself will tell him that you care about him. If you've gotten into the habit of not dressing up anymore than start dressing up again. If you were never the type to dress up, then do it once in a while. If you were a size X when you met then a size X is what he should get. The same goes for him.
If finances allow, take a weekend away together. If they don't allow, then continue to do new things with each other - go to different places: restaurants, local attractions, etc. that neither of you have been to and try activities that you haven't done yet. Doing some fun but routine things helps keep you bonded too. For instance, my hubby and I love to play basketball with each other and it gets those feel good hormones pumping which leads to...well, you know.
Spending time apart is also helpful to keeping the love alive. That old saying, distance makes the heart grow fonder is often true for relationships. I'm not saying to do this in a manipulative way like suggesting a short-term break up. Taking time to do things with your own friends or going away for a week to visit family or vacation with friends is often good for you and your relationship. It gives you time to miss him and him time to miss you. Also, doing and learning new things without him gives you topics to bring up in conversation.
I know you probably think you know everything there is to know about him but it's not true. It's been nearly eight years and I'm still learning about my hubby. While men aren't typically huge talkers, talking is one thing that makes us women feel closer to friends and the men in their lives. Sit down once in a while over some wine or a nice meal and talk about all kinds of things. Ask meaningful questions about him to gain a deeper understanding about who he is. Don't make it an interrogation though - relate a story or your own opinions on a subject to share something first so he doesn't feel like you're prying and he'll open up.
Do little loving things for him once in a while. We both work but every so often I get up extra early to make him a "King's feast" to bring to work for lunch. I put it in his car with a nice note before I leave to go to my own job. Men like receiving gifts too from time to time and I get him little things throughout the year because I know he'd like it or needs it. He does these things for me as well.