I'm not very good at remembering to exercise, but this past semester I added a few things to my regimen, even if only for a few weeks.
My first show this spring, the other ASM, SM and I instated "SM Situps" before rehearsals-it never took our full half hour to sweep the stage and get rehearsal props out, so once all of that was done we'd do an ab workout while we waited for the cast to arrive. Some of the actors walked in on situps one night and joined us, and for the next week or so a few of them would get to rehearsal early and our situps would start warmups. This fell to the wayside once we got into tech, but it was nice to have an allotted time each day for crunches.
My second show, the cast were huge fans of Sun Salutes, and ended warmups with them every night. During early rehearsals I typically had too much to do to join them (this was the show with nomadic rehearsals across campus, never the same room setup twice for a few weeks), but once we got into a fixed space and setup became normalized, I made a point of joining them at the end of vocal warmups for a series of Salutes. Not only are they a great stretch, but we did them back to back, gradually building up speed, so they get your blood pumping and are also great for focusing. I still try to do a set of Salutes every day--first thing in the morning tends to be the best time, I've found.
I also swear by my water bottle and either ice water or Emergen-C--having something to hydrate me 24/7 saves me so much trouble and money, as I'm not buying soda/juice/coffee/tea/etc at every meal.