My CP won't eat any later than 3 hours before she competes and she tries to eat light when/if she does eat. If she's full or eats heavy, greasy foods she's sluggish and it really affects her performance. Some examples of what she eats early are: eggs and whole wheat toast or english muffin, small salad with grilled chicken and fat-free dressing, banana (for potassium - it helps muscles perform) with a handful of nuts or PB, protein bar with at least 12g protein.
To help with blood sugar issues make sure you're eating fiber and protein. Those will help keep your blood sugar level much more steady than sweets or "white" carbs - those make your blood sugar spike high and then crash. Always have a protein with your carbs/sugars, too. So, if you eat a fruit have cheese or nuts with it, etc.