To determine the extent to which Veolia Environnement should utilize hybrid bonds relative to S&P Global Ratings' cap, we must first calculate the company's current usage of hybrid securities as a percentage of its total adjusted capital. S&P defines total adjusted capital as total debt plus equity, and limits the equity credit given to hybrids to a maximum of 15% of this total.

1. **Calculate Equity:**
Using the 2023 balance sheet data:
- Equity Attributable to Owners of the Parent: €12,254,700,000
- Noncontrolling Interests: €2,612,200,000
- Total Equity = €14,866,900,000

2. **Calculate Total Debt:**
Total debt typically consists of financial borrowings (both current and non-current). Based on the 2023 liability breakdown:
- Noncurrent Financial Liabilities Excluding Concession Liabilities: €19,692,100,000
- Current Financial Liabilities Excluding Concession Liabilities: €6,521,400,000
- Bank Overdrafts And Other Cash Position Items: €213,600,000
- Total Debt = €26,427,100,000

3. **Calculate Total Adjusted Capital:**
Total Adjusted Capital = Total Debt + Total Equity
Total Adjusted Capital = €26,427,100,000 + €14,866,900,000 = €41,294,000,000

4. **Identify Hybrid Securities:**
From the equity statement and balance sheet, hybrid bonds correspond to the "Titres Super Subordonnes A Duree Indeterminee" (Deeply Subordinated Securities). 
- Total Hybrids (2023-01-01) = €3,496,300,000

5. **Calculate Current Hybrid Utilization vs. S&P Cap:**
S&P Maximum Hybrid Allowance = 15% × Total Adjusted Capital
S&P Maximum Hybrid Allowance = 15% × €41,294,000,000 = €6,194,100,000

Current Hybrid Percentage = (Total Hybrids / Total Adjusted Capital) × 100
Current Hybrid Percentage = (€3,496,300,000 / €41,294,000,000) × 100 ≈ 8.47%

6. **Determine Relative Utilization:**
The company is currently utilizing approximately 56.4% of its S&P maximum allowed hybrid capacity (8.47% / 15%). This indicates that Veolia has a substantial amount of headroom remaining under the 15% cap, having only crossed the halfway mark. 

Given the options to characterize the extent of their hybrid utilization relative to the cap:
- 0% and 25% are too low, as they have issued well over half a billion to billions in hybrids (utilizing over half the cap).
- 75% and 100% are too high, as they still have significant unused capacity (remaining equity credit room of nearly €2.7 billion).
- 50% is the most accurate representation, reflecting that they have moderately utilized their allowable limit, falling closest to the exact ~56% threshold. 

<answer>50%</answer>