請問 2006 Toyota, 添加刹車油，冷卻水一定要用手冊規定的品牌嗎? Not Really

The brake fluid is DOT3. It is not Toyota specific, but rather a generic, standard fluid sold in  auto parts stores, Walmart, etc.

The coolant is Toyota specific SLL (super long life) pink coolant. Older models use Toyota specific LL red coolant. Even older models use green coolant. The service specification says Toyota recommends SLL coolant. So it is not a must.

The recommended coolant/water ratio is 50/50, but can be 40/60 or 60/40. The Toyota SLL coolant is 50/50 pre diluted. Adding a little bit of other coolant usually is fine, but is not recommended. If the coolant level in the recovery bottle is a bit low, just add a little water. That's what the shops do in the routine maintenance.