1. Like it's imagery, plastic bouquets is a declaration of love that is cheap and somewhat insincere.
2. Plastic bouquets are acts of love that are cheap or easy and thus do not have the meaning they are intended.
Showing up at her doorstep in the middle of the night was sweet but she couldn't help feeling as if it was all plastic bouquets.
Despite his sincere and desperate love, his actions all seemed like a plastic bouquet and he was left brokenhearted.