Here is a list of pleco safe fruits and veggies!
Your pleco might not eat all of them but it’s good to try for variety. The two plecos that I knew got wafers at least once a day and a cucumber/cucumber slice a few times a week (that I remember, I didn’t see them every day). Cucumber isn’t the most nutritious veg, but they loved it. (Zucchini/courgette is more healthy.)
Please research your plecos.... not just on size, but also their diet! Some plecos are strictly vegetarian, some are omnivores, some are carnivores, some are literally algae eating machines (no pleco survives on algae/scavenging on the bottom of the tank alone). All plecos like a good algae wafer. All benefit from driftwood (and wood is required if you have a Panaque, Panaqolus and a few specific Hypostomus).
I’ve never tried any of this: Some seafood is also pleco safe (I’ve seen plecos eating shrimp a few times on youtube, not sure completely how safe it is), and there’s gel food you have to prepare like Repashy (they have some amusing names for their fish food).
Planet Catfish has a great article on this as well: part 1 and part 2
(No endorsement of anything in this post, just feed your pleco the right food!)