Light and fairly quick recipe for the grill, although you do have to factor in some marinating time. The version I came across originally called for seitan chunks, (found on http://www.wailana.com). Prep time doesn't include marinating.
Gently press out as much water from your tofu as possible. I do this by placing the block of tofu in a towel and leaving a weight on top to press down on it for about 10 minutes (can of beans on a plate works well). Pat dry.
Mix the marinade ingredients together in a medium saucepan. Bring to a gentle boil and stir well - the sugar should be dissolved. Simmer for about 10 minutes, you want the sauce to be quite thick, but if it's too thick you can add a bit of water. Set aside to cool.
Assemble the kebabs, alternating pieces of seitan, pineapple, and bell pepper on the skewers, leaving space at the base for holding the skewer. You should be able to fill 6 skewers.
Pour the cooled marinade over the skewers, rolling around or using a brush to coat every piece. Leave to marinade for about an hour, or better even longer if you have the time. Great if you can do this prep the day before.
Grilling - remove the skewers from the marinade and place them a preheated barbecue grill. Leave about 3 minutes per side so you get nice grill marks and the veg are nicely browned. Baste as you go with some of the leftover sauce. You could also prepare under the broiler.
Heat up any remaining sauce and serve alongside the skewers.