It depends. I almost always take someone with me. Sometimes I pass up shops because the reimbursement falls too short of the cost to make it worth it to me. Or sometimes I do dine alone. I seldom take shops that require me to pay parking unless parking is reimbursed. Since you have not mentioned any clients OR MSCs, I will use a couple of clients as examples.
When I do a Wingstop, the reimbursement is $20 and I can feed two regardless of time of day. When I do a Buffalo Wild Wings, the reimbursement is $18 with $5 pay. If we eat at lunch, there is a Fast Break Menu that gives you an entree and a side. By drinking water instead of a paid beverage, the total comes to right at $18, including meals, tax and tip.
A lot of burger places, like Five Guys allow reimbursement for one. At Five Guys, I can stay within the reimbursement amount. Any pay I receive goes toward paying myself for my guest's meal. Some burger places, like Shake Shack, require that if you take a guest, the guest's meal is on a separate ticket, and reimbursement is for one diner.
Back in the day when I used to shop Cheesecake Factory, a dinner shop was a $40 reimbursement. That was barely enough for 2 meals (the smallest), tax and tip with no beverages. Because my family loves Cheesecake Factory, I usually took those shops and all 3 of us went. Our total for 3 adults was usually about $72 with tax and tip and only one paid beverage, or $90 with 3 beverages and appetizer. We significantly went over the reimbursement, and I considered the $40 like a "half-price coupon." That is the only restaurant I can think of that I was willing to add significant money to eat.
Usually, when I contemplate taking a food shop at a new-to-me place, I Google the restaurant and look at the menu. I look to see what the menu options are and how much everything costs, figuring whether the reimbursement will cover what I want to eat. I make my decision from this, depending on whether I like the food or not - I never take shops if I don't really like what I'm eating, because, since the reimbursement is part of the payment for my services, it would have no value to me if I didn't like it.