I have some rice, vegetable curries, fish or omlete for lunch. My blood sugar after 2 hours of lunch is usually 140-160mg/dl (7.8 to8.9 mmol/l). Usually very sleepy about 45 minutes after lunch.
Try testing your blood glucose at around the time you feel tired (45mins) rather than 2 hrs post-meal. Let us know what numbers you find. You may be experiencing dumping syndrome - hypo followed by a rebound hyper. Because 7.8-8.9 mmol/l 2 hour post-meal reading is fairly normal and shouldn't cause the sleepiness. If it was above 10 maybe but not really at your levels.